Many parts such as the ones used in automotive structures are manufactured using a hydroforming process. The hydroforming process requires large presses up to 5,000 tons to hold the hydroforming die close during the hydroforming process. These presses are large, expensive, require large amounts of energy to operate and require special and expensive installations, yet the work is done using the hydroforming pressure not the press forces. In an effort to reduce the automotive vehicle weight, high strength steel is being used, which means larger hydroforming presses are required.
Processes such as hydroforming process requires large presses to clamp the die in place while forming is done by other means such as applying internal pressure to form the part.
As shown in FIGS. 2a and 2b, the hydroforming technique according to the prior art includes providing a die 10 having a lower portion 12 and an upper portion 14 which combine to define a die cavity 16. The upper portion 14 is moved generally downward into a closed position forming a die cavity 16 over a round tube 22. Side plugs 18 and 20 are then moved sideways to engage the tube 22, to seal both ends of tube 22, and a hydraulic pressure source is connected to the interior of tube 22 through an opening 24 inside plugs 18 and 20, thereby expanding tube 22 until it conforms to the shape of the die cavity 16.
The force F required to keep the die 10 closed varies according to the size of the tube 22 and typically is in the magnitude of thousands of tons. In order to supply the force F a large press is used to keep the die 10 closed. For example, the press typically provides a force F of 5,000 tons or more. With reference to FIG. 3, the prior art press is relatively large and expensive. The prior art press often is mounted to a subsurface structure, which is relatively expensive.